Rotation matrix problem, besides rotation my object gets translated too

Rotation matrix problem, besides rotation my object gets translated too.

Matrix m = new Matrix();   
m.SetRotate(new Vector(0, 0, 1), Math.PI / 4);  
m.PrintMatrix();    
for (int i = 0; i < 6; i++)    
{  
_spaceship.VertexPositions[i] *= m;  
}

1. I create an identity matrix.

2. SetRotate makes it a rotation matrix, for rotation pi/4 around z axis.

3. I printed more matrices to check if SetRotate does work, it does indeed, so SetRotate does it's job well, something else must be causing the problem.

4. _spaceship is a sprite with 6 vertices(two triangles), and each of them i multiply with the rotation matrix. VertexPositions stores Vectors for each vertex position.

So the rotation matrix is fine, i have checked the vector ma开发者_JAVA技巧trix multiplication also fine, I don't understand where that extra translation could come from. My object does get rotated pi/4, but it gets translated X:-14.1421356237309, Y:-16.6170093578839, Z:0, and it is supposed to be all zeroes X:0, Y:0, Z:0 just like before the rotation.

---

Are your spaceship's vertex positions already offset? If you want to rotate your model around it's center, make sure that the model vertices are relative to the center.

---

You probably need to normalize your vec3 before making the rotation.